Scientific calculator performs 419 functions and features Direct Algebraic Logic (DAL) to simplify the entry of equations. DAL allows students to enter the elements of an expression in the exact order they appear in the textbook. The Multi-Line Playback makes scientific equations easier for students to solve because they can "playback" the expressions and substitute new numeric values. Calculator also includes differential and integral Calculus functions; physical constraints; metric conversions; a large 12-digit, two-line LCD numeric screen; and nine independent memories. The hard slide cover protects the calculator so it can withstand frequent use. Calculator is recommended for general math, pre-algebra, algebra, trigonometry and biology. PTA approved tests include AP Chemistry, AP Physics, PSAT/NMSQT, SAT I, SAT II, Math IC, and Math IIC. Twin power calculator runs on solar power and battery power for low-light conditions.